Method of acid treating a viscous hydrocarbon oil



B. G. JONES ErAl. 2,400,298

l,METHOD OF ACID TREATING A VISCOUS HYDROCARBON OIL May 14, 1946.

Filed Feb. l2, 1944 2 Sheets-Sheet 1 wNY mm 3.x l@

Acxuxrv op o\\ LEAvxNG sEcoNb CEHTRIFUGE May 14 1946 B. G. JONES ETAL 2,400,298

METHOD 0F ACID TREATING A VISCOUS HYDROACARBON OIL Filed Feb. 12, 1944 2 S11ee'r.s-Shee1.y 2

REACTION 'HNE BETWEEN CENTRIFUGES MNUTES n @rTQ/vy fing.A description;

Patented May 14; 1.946

METHOD` F ACID TREATING A VISCOUS HYDROCARBON OIL Benjamin G. Jones, Associated, and Leslie` H.

Sharp, Martinez, Calif.; assignors to Tide Water Associated Oil. Company, San Francisco, ,Cali1'.,l

- a corporation ofDelaware l' "l Application February 12, 1944, SerialNo. 522),()78

` L11 claims. (c1. 19e-40)v This invention relates to use the sulphuric acid treatment ofV lubricating oil and similark viscous oils andl to the subsequentremoval ,therefrom of the spent acidVV and other reactionproducts. It

hasl for` its-.principal object. the separationof rey action productsv from acid treated viscous oil stocks in a highly emcientmanner.

Another object is toreduce the quantity of yacid reaction products normally contained in sulphuric vacidtreated lubricating stocks prior to neutralization:` and thereby reduce` the quantity of alkali neededfor neutralization and to improve theoverallieiiiciency of the'neutralizing procedure.

Al further object is toimprove the qualityr of sulphonicl acids derivedfrom acid treated lubricating-oils.

Other Aobjects will'be apparent from the follow- In; the manufacture' of, lubricating oils it is commonl practice to` contact lubricating stocks with sulphuric acidi (of a strengthV from about 66? B'. uptoand'including fuming acid), gener- .ally at, slightlyV elevated temperatures, for sufi-lcientV time tovpermit theacid to react withrthe more reactivefconstituentsof the oil after which the spent acid, or 'acidisludga is removedand the oil'is` then-neutralized,- With an alkali and subjectedA to 'Whatever further. finishing treatment maybe desired', such. as redistillationY contact with fllteringnfiedia, etc.

For, decades such treatment was carried 'out' bybatchY operation, usually. 'in open vessels and with: air-agitation, following vwhich the sludge wasfpermittedvtosettle by gravity,Y usually with the additioneofzasmallamount of Water to hastenY thervcoagulationzand settling of the sludge. Such practice was tedious, messy1 and wasteful, ofboth timerandv materials. In'. modern practice the oil isI agitated with,` thei acid., in eilicient v.mechanical devices. following.y whichl thesludge` is separated by; centrifuge hovveven-the neutralizationis genera-lly` carried outffbyV batch operation, because Y of the carefulgattention required of the operator-to avoid-excessivefemulsions.which tend to occur at this stage; of the-processasfa result ,oi-'the formaticniof. soapsoi' theoilfsolublesulphonic acids. It is;to..-thispractice off separating the sludge with centrifugesv that'. the-.present inventionr is morev particularly related. A

' A A'ftertreatmentwithisulphuric acidand/b'efore l fled as .Iollows:;

such as naphthenic acids, cresylic-acids and phenols. tMost oftheseY are probably reacted with the sulphuric acid and, therefore, are present in the form'of their sulphonic derivatives.

(2) Oil-soluble sulpho-acids of various types. For convenience these will be referredto as sulphonic acids.

' (3) Suspended, oil-insoluble, sulpho-acids together with unreactedvsulphuric acid. These will y be referred to as sludge.v (4) Dissolved sulphur dioxide. v

The centrifuging removes the` sludge acidity described under item'( 3)! above and it is the purpose of the subsequentneutralization to remove the remaining acidity. The resulting soaps of the oil-soluble sulphonic acids are advantageously recovered andbecomean important by-product. However,A these soaps areV powerful emulsifying agents andtheir presence duringfthe neutralizing rsteps causes, at times, great difficulties -in separating the same-from the oil. As a result there is usually a substantial' amount of oil which'is removed with these soaps representing a-loss in yieldof nished lubricating oil,

The invention provides'a means wherebythe more unstable of the oil-soluble sulphonic acids may be removed from the oil prior'to neutralization; thereby greatly reducing the amount of alkali-expended'in neutralization, markedly improvingatlieV quality of. the 'sulphonic soap byproduct produced by eliminating" the more unstable elements, and,` as the soaps of the more unstablefacidsfappear to ybe the greatest emulsion producers during neutralization,Y greatly alleviating the emulsion troubles as well as producing greateryields of nished lubricating oiland less contamination of thesulphonicsoap product by the oil. Further, it has beenfound that the more unstable of the sulphonic acids are the more corrosive and their presence vduring neutralization in iron vessels results in undesired iron contamination of the sulphonic soap by-product. This contamination is reduced by removing these acids 'Briefly' the invention comprises .providing a time interval, after centrifuging the acid sludge i'romthe acidtreated oil, forthe more unstable oil-soluble sulphonie 'acids to polymerize and become oil-insoluble and-subsequently recentr-ifuging toremove the insolublematerial so formed. It has been found that the voil-soluble 'sulphonic acids'remaining inthe oil aftercorplete separation of'sludge are of two kinds:` (a) those which (1); ,OrganicacidsVVV originally present inthe oil, 55' are relatively stable and (b) those which, though originally oil-soluble, polymerize in time to form cil-insoluble sludge-likematter suspended in the oil in iinely divided form. Under temperature conditions normally occurring at this stage of the treatment (i. e. between about 80 and 160 FJ, this polymerizing reaction appears to lbegin as soon as the sludge is separated fromA the oil and continues for about 45 minutes after which further polymerization is so slow as to be relatively unimportant. Accordingly, for best results, a time interval of at least about 45 minutes should be given to permit as great a quantity as possible of these unstable compounds to polymerize; howl ever, with a time interval of as lo w as ten minutes a noticeable degree of polymerization occurs which may be sunlcient, under some circumstances, toreduce the amount ofunstable oilsoluble sulphonic acids in a desirable degree.

As the quantity of sludge-like matter 'formed by the polymerizing reaction is only minor as compared with the quantity of acid sludge produced by the original acid treatment of Ythe oil, the throughput rate of the centrifuge during the recentrifuging step may be maintained considerably higher than that required for efilcient separation f sludge in the first centrifuging step, or, if desired, -fewei or smaller centrifuges may be used for the second separation.

In carrying out the invention it may be convenient to pass the oil, after removal of sludge in the first centrifuging operation, to a storage tank wherein sufllcient time is Vallowed for the polymerizing reaction, and then,\at intervals, to discontinue the acid contacting operations and to recentrifuge the oil from the storage tank in the sameV centrifugethat was'used for the removal v of the primary sludge. It is preferable, however, to provide two centrifuges, or sets of centrifuges, with a time-tank ot sulcient size so that the oil may continuously be passed from the nrst centrifuge `to the time-tank and continuously withdrawn from the time-tank and charged to the second centrifuge.

vThe invention may better be understood by reference to the drawings, Fig..1 or which illus- .trates in diagrammatic form a typical sulphuric acid treating plant with additions suitable for practicing the invention. Raw distillate to be treated is charged by pump 3 from storage tank I and line 2 through line l and through heater 5 provided with suitable heating means, indicated by steam-coil 6, to raise the temperature of the oil to'thedesired degree for treatment. Commonly, temperatures of about 80 F. to 160 F. are employed, although, in various instances, higher or lower temperatures may be employed depending on the stocks treated and the degree of treatment desired. The heated oil leaves heater through line 1 and passesito mixer Il whichA may advantageously be a centrifugal pump. Sulphuric acid from storage tank 9 is charged by pump I0, at the desired rate for lthe required treatment, through line Iljand injected into the oil in line 1. The mixture of acid and .oil is thoroughly mixed by, mixer 8 and charged through line I2 to treating tank I3 which is of sumcient size to permit a desired time of contact (generally from loto 60 minutes) between the acid and oil. After sufiicient Contactin tank I3 the oil passes to pump I4 which charges the oil to centrifuge I1 through lines I5 and I3. In centrifuge I1 the oil is rapidly separated from the acid sludge, the oil leaving through linev I9 and the sludge through line I3.

As described thus far the process is convenrtional and the oil leaving centrifuge I1 is conventionally passed directly to the neutralizing step and thence to whatever further finishing is desired. The various apparatus mentioned, not being a part of the present invention, may be varied.V For example, mixer 8 may be of various forms such as an orifice mixer. or it may take the form of agitating devices placed in tank I3. Likewise, tank I3 may contain baiies, or the like, to assist in contacting the acid and oil. A convenient means for maintaining contact of the acid and oil is to circulate a portion of the oil from the bottom to the top of tank I3 through pump Il and lines I5 and 20. Various rates of acid and oil may be used and the time of contact may be varied. Treating of the type here involved isusually conducted at an acid rate of about 20 to 100 pounds of acid per barrel of oil and a time of from 10 minutes to 1 hour is usually employed.

According to the invention the oil leaving centrifuge I1 iiows through line I9 into a time-tank 2l wherein a level of oil 22 is maintained (by regulation of valve 23) at a sufiicient height to cause the oil to remain in the time-tank a suillcient time, in excess'of 10 minutes and'pref'erably at least 45 minutes, for the least stable of the oilsolublesulphonic reaction products to polymerize. After the required'time in time-tank 2I the oil leaves through line 24 and is charged by pump 25, through line 26, to centrifuge 21 wherein the polymerized sulphonic products are separated and ejected through line 23, the puried oil leaving through li'ne 29.

The treated oil leaving centrifuge 21 through line 23 is subsequently subjected to neutralization with alkali, preferably'an aqueous solution of caustic soda. As stated prior, the neutralizing step is preferably carried out in batch operation 40,

is provided. As illustrated in the drawings, oil

and to permit the same a suitable surge tank 30 is withdrawnl in batches from surge tank 30 by pump 3| and charged through lines 32 and 33 to agitator 34 which is equipped with suitable means for agitation, indicated as agitation with air' en- .tering through line 4I) controlled by valve 4I. A

required amount of caustic soda or other alkali is introduced through line 35 and valve 36 and, with sufilcient agitation,rthe alkali combines with the various acids present in thev oil, including sulphonic acids, forming an aqueous solution of the alkali salts of the acids. After proper agitation the mixture of oil and alkali is permitted to settle following which the spent alkali is withdrawn through valves 31 and 38, following which the treated oil is withdrawn through valves 31 and 39. .The treated oil may be subjected, if desired.

hto further processing such as clay treatment or redistillation. vThe spent alkali may; if desired. be processed according to known methods for the recovery of sulphonic soaps.

The neutralizing procedure is'more or less conventional and, in general, is similar to that conventionally applied to oil leaving centrifuge I1.

Accordingly, the neutralizing may be varied without departing from the spirit of the invention. It is to be noted, however, that when the process of the invention is employed the separation of the aqueous mixture of alkali salts from the oil takes place more rapidly and more completely with arless tendency toform emulsions,- and, accordingly, less oil is Vretained by the spent Aalkali resulting in greater yields of nnished oil and less contamination by oil of recovered sulphonic soaps. Likewise, when the invention is practiced,'due to for use as transformer dielectrics,

' four 'centrifuges operating in parallel.

Y a time-tank wherein the the presence of less acidity in the oil, a less amount of alkali is required for neutralization.

. Fig. 2 ofthe drawings is a chart illustrating.V for a specific treatment of a specific oil, the

amount of acidity remaining in the oil yafter the second centrifuging ior various reaction times between the primary centrifuging, Vwhereinthe acid-,sludge was removed, and the second centrifuging. wherein the polymerized sulphonic products were removed. In the chart the acidityoi the oil is"expressed by the pounds vof NaOH required to neutralize one barrel of oil. From the chart it -is seen that a noticeable reductionin acidity occurred Vwith a reaction time of minutes, but thatior optimum results a reaction time of at least 45 minutes shouldbeused.` In theforegoing description the term polymerization has been 'used'tospecify thereaction occurring among the oil-soluble sulphonation products following the initial. removal of acid sludge. As the reaction the term is used in a broad sense to denotev the Iormation'of oil-insoluble bodies by a Vreaction involving unstable oil-soluble sulphonation products. It is not intended to limit the term to certain specific chemical-reactions to which the term is sometimes applied inthe art.r

While the invention is notr restricted to any specific lubricating oil stocks undergoing treatment with sulphuric acid, it is particularly adapted-to the sulphuric acid treatment of lubricating is not well understood,

therconventional procedureV omitting the timetank and second centriiuges: '1

ggoes Convening to v tional i... im@

kube distillate charged' (bbL/day) 1, 000 1, 000 cid treated oil from ilrst oentriiuges (bbl./day) 7 40 ,Y 740 Acid trealed ,oil from second oentriiuges f 28 ay Oil charged to agitator (bbl.) 728V 740 4 B caustic soda used (lbs. NaOH) 500 940 Theoretical caustic soda required (lb 460 890 Neutral oil recovered (bbl.) 710 `703 Crude sulphonic soa s (bbl.) i8 37 Oil in crude sulpho c soaps 50 75 FezOa in crude sulphonic soaps .002 .05

Time required for spent caustic to settle from I neutralized oil (hr.).. ..l.-..; B 18 .Weolaimt f 1.- The method ofacid treating'il'which comprises: contacting a viscous hydrocarbon oil with concentrated sulphuric acid foratimeand-'at' a temperature sutlicient4 to cause theI acid to react with unstable constituents of the 'oil to form oilsoluble sulphonation products p and oil-insoluble acid sludge, centrifuging the"c0ntacted-oi1 toremove. said sludge, maintaining' thesludg'e free oil without further treatment for a period 'of time between ten minutes and aboutY oehoursui- Vcient'to cause unstable oil-soluble constituents stocks derived from California crudes and like oils which contain relatively large amounts of materials readily `attacked by sulphuric acid. As used herein the term lubricating oil" is intended to refer to viscous oils having a viscosity in excess of 50 seconds S.y U. 100 F. as contrasted with naphthas and kerosenes. Embraced in the term, as so used, are viscous oils primarily intended lnsecticidal sprays, and the like.

Following is an example of the practice of the invention in combination with commercial sulphuric acid refining:

A lube distillate derived inga crude oil and having a Saybolt Universal viscosity of 62 seconds at 210 F. was charged at the rate of 100i) barrels per day to a continuous from California Coal- `acid treating plant wherein the oil, heated to a -mers of the more unstable oil-soluble sulfonation products. From the` time-tank the oil was charged to a battery of two parallel centrifuges similar to those used for the acid-sludge separation. The acid oil was then charged to a 1000 barrel agitator and contacted 2 to 3 hours with an excess of 4 B. caustic soda solution, after which the mixture was allowed to settle,l the spent caustic containing sulphonic soaps was withdrawn, and the neutralized oil was passed to storage. Crude sulphonic soaps were recovered from the spent caustic by salting out with strong caustic soda solution. 'I'he following table gives data obtained in this run compared with data for a similar run made in the same to polymerize and form oil-insoluble rbohlies,` centrifuging said bodiesfrom saldoill then contacting the'oil withexcess alkali to absorb contained acidic bodies and removing the contacted alkali from the oil.

2. The method of claim: 1 k wlie'reirrs.aid period v v` of time is vatleast about 45 minutes;

apparatus by contacted with "aqueous caustic soda. A

L3'. The method of claim 1 wnereinjlsaid'eikaii is wherein aistream of viscous hydrocarbon voil is mst contacted with concentrated sulphuric acid forming oil-:soluble sulphonation products and oil-insoluble acid sludge and the stream of oil is then subjected to a centrituging step to remove the acid sludge and wherein the sludge-free oil is later contacted with an alkali to absorb and remove oil-soluble acidic substances, the combination of steps which comprises: subsequent to said centrifuging step 4. In an oil treating process and prior to contacting with alkali, providing a time interval between ten minutes and about one hour suillcient for unstable oil-soluble sulphonation products in said oil stream to polymerize and form oil-insoluble bodies and then centrii'uging said bodies from said stream.

5. In an oil treating process wherein a stream oi viscous hydrocarbon oil-is continuously contacted with concentrated sulphuric acid forming Voil-soluble sulphonation products and oil-insoluble acidsludge andsaid sludge is continuously and mechanically removed from the oil and wherein the sludge-free oil is later contacted with an alkali to absorb and remove oil-soluble acidic substances, the combination of steps which comprises: subiecting the acid treated oil to a iirst centrifuging step to remove acid sludge, then,l after a period of time between ten minutes and about one hour suiilcient for unstable oil-soluble sulphonation products in said oil to polymerize and form oil-insoluble bodies but prior to contacting with alkali, subjecting the oil to a second centrifuglng step to remove oil-insoluble bodies so formed.

6. In combination with an oil treating process wherein a stream oi' viscous hydrocarbon oil is concentrated sulphuric acid to` sludge .free voil 'to remain in acid condition for a period betweenjten .minutes `and about one hour suflicient for unstable oil-soluble sulphonation `products to polymerize forming Y oil-insoluble bodies, lthen centrifuging said bodies from said oil. i

'7. The process of removing unstable compounds from oil which comprises: causing a sulphuric acid vtreated viscous hydrocarbon oil containing unstable loil-soluble :sulphonation products to remain lin the 'absence .of `acid sludge for a. substantial period of time in the `order vof one hour suflicient for .said products Y to polymerize and .form bodies insoluble iin theoil, then vcentrifuging said oil to remove said'bodi'es. Y

'8.v The process of removing unstable `compounds vfrom oil which comprises: causing a'sulphuric .acid treated viscous hydrocarbon oil containing unstable oil-soluble sulphonation products tovremain in the ,absenceof acid .sludge for a substantial period of .time in the order of one hour sumcientjfor said vproducts to polymerize and form bodies Vinsoluble in the koil, then mechanically removing said bodiesfromrsaid oil.

, cause the jac'id to react with-constituents of the --oilto form oil-soluble sulphonationlproducts and oil-insoluble acid sludge, and wherein the acid sludge isthereafter-,centrifuged from `the oil, the V.method 'of `removing unstable oil-soluble sulphonation products which comprises:v causing the one hour sufficient nto cause unstable oil-soluble constituents to polymerize andfform oil-insoluble bodles,"centriiuging said bodies from saidoil, then contactingf'the loil with excess alkali to absorb contained acidic bodies and removing the contacted alkali fromY the oil.'

10. The method of acidr treating oil which comprises: contacting a viscous. hydrocarbon oil with concentrated sulphuric acid for a time and at a temperature sulcient to cause the acid to react lwith unstable constituents of the oil to form oil-,soluble sulphonation products and oil-insoluble acid sludge, centrifugg'ng the contacted oil'to remove said sludge, maintaining the sludge free oil withoutfurther treatment for a period oi time between ten minutes and about one hour sufllcient to cause unstable oil-soluble constituents to polymerize and form oil-insoluble bodies, irnmedil ately separating substantially all said bodies from said oil, then contacting the oil with excess'alkali to absorb contained acidic bodies and removing Vthecontacted alkali from the oil.

g 11. The vmethod of acid treating 011 which comprises: contacting a viscous hydrocarbon oil with concentrated sulphuric acid for a time and at a temperature sufficient to cause the acid to'react with unstable constituents of the oil to form oilsoluble -sulphonation lproducts and oil-insoluble acid sludge, immediately separating substantially all the sludge from the oil, maintaining the sludge Vfr'eeV oil without further treatment for a period 0I time between ten minutes and about one hour suillcient to cause unstable oil-soluble constituents to polymerize and form oil-insoluble bodies, immediately separating substantially all vsaid bodiesfrom said oil, then contacting the oil with excess Valkali to absorb contained acidic bodies and removing the contacted alkali from the oil.

BENJAMIN G. JONES. LESLIE `H. SHARP. 

